magnetos don't have " wiring" as such. You are simply spinning coils of wire inside magnets, generating electricity. Some wonderful stuff with primary/secondary coils and the contact breaker generates a spark.
The only "wiring" is the HT lead to the spark plug.
i'd change the spark plug first. Then i'd check the points, ensuring the right gap and that there is NO MUCK on them. Then it's testing output from end of lead back to the pickup. Then it's pickup off to check it's not worn or bust. Clean the slip ring track
John "Josh" Nash firstname.lastname@example.org AOMCC No.4119 2009 royal Enfield,1978 t140 bonneville, '67 CJ750, 196-ish Ural M62 outfit, 1960 k750, ''51 kH500, ''49 soon to be Ariel bobber, 47 VH twinport, '44 Ariel WNG, '43 Ariel WNG, ' and piles of rusty scrap ....
thanks. i was interested in a diagramme 'cos i frankly know now't about mag/dynos but there is what looks like a grub screw and housing on the lower left hand side of the unit just below the manual a/r cable entry - it has no wire in it so i guess it is not used or maybe its supposed to go to earth?
i was also hoping for a diagramme just in case i need to trace any of the wires in the future.
as far as the 'lost' spark is concerned, the bike was starting/running well but i deceided to change the plug and clean the points in situ using a thin diamond file (set to 15thou) both of which i did and it would not start, taking out the plug there was no spark. left it to the following day to have another go and without doing anything just kicked it over and there was a big blue spark?!? its now starting and running like before - guess this is one of those times when you never get to the bottom of what happened!
Hi Brian, The grub screw in question is for an earth wire to the frame to provide a return for the dynamo current and spark. Should not be necessary as the magdyno is firmly bolted to the engine plate platform but it is provided in case of paint preventing a good earth I think.